1. The Field of the Invention
The present invention relates generally to the interface between physical/electrical media connectors and a communications card in a computer system and to communication devices capable of receiving a media connector. More specifically the present invention relates to an improvement in the electrical connection therebetween.
2. The Relevant Technology
The field of transmission of data by phone lines or network cables is a rapidly expanding field. Users of personal computers in particular are finding such practice to be of great value.
For example, there are numerous public and private networks and databases which store data or programs. Absent the ability to send and receive data over telephone lines through a modem, a user is relegated to relying upon the exchange of discs or tapes in order to receive data suitable for use with their computer.
Similarly, companies performing tasks that are integrated are aided by local area networks ("LANs") which permit personnel to exchange electronically retrievable data. The ability to freely transfer data and information from one computer to another computer over a telephone line may dramatically increase productivity and reduce overall production time.
To translate the binary code utilized by a computer into signals capable of being transmitted over the telephone lines, modems have been developed to translate and reconfigure binary signals into analog signals capable of being transmitted over telephone lines. For conversion of signals to take place, a modem must be placed between the computer generating the binary signals and the telephone line capable of carrying the analog signals.
Typically, in today's practice, a modem at the transmitting computer end of a telephone line receives binary digital data from the computer and converts the binary code received from the computer into modem frequency signals. These modem frequency signals are then transmitted over the telephone lines to a receiving modem at the receiving computer.
The modem at the recipient's end then converts the modem frequency signal back to binary digital data characters and inputs the data characters to the input port of the receiving computer.
As today's modems serve to provide a compatible interface between the phone lines and the computer, the Federal Communications Commission ("FCC") and telephone companies require an interface to moderate all signals or energy being input into the phone lines. This interface protects the phone lines and systems from damage, thereby ensuring the integrity and quality of transmissions over the phone lines.
A required part of this interface is a Data Access Arrangement ("DAA") circuit. The DAA circuit provides an impedance match and also serves to isolate the modem and the computer from transient signals and other disturbances coming in over the phone line. The DAA also protects the phone line from disabling influences emanating from the computer or the modem.
For example, damage would occur to the telephone system if instead of transmitting frequency signals, DC power was transmitted over the phone lines. Because the modem is attached directly to the phone line, the modem must incorporate the required FCC interface and must comply with any requirements imposed by local telephone companies.
The ubiquity of the telephone and the need for interactive systems throughout the world have caused standards to be established for the components of a telephonic system. Standardization allows telephone systems and devices using those systems to be interchangeable. The components of the telephone that are most thoroughly standardized are physical/electrical media connectors.
Physical/electrical media connectors are used by almost all telephone companies throughout the world for many applications, the most important of which is interconnection of telephones with telephone lines. For this reason, stringent standardization of connectors is required if compatibility and interactivity is to be realized.
One popular physical/electrical media connector used in the United States of America is the RJ-11 4-position miniature modular plug physical/electrical media connector. The RJ-11 is used between the telephone line and the telephone itself
Unfortunately, because of the physical and electrical differences between the many pins of the peripheral ports associated with the central processing unit of a computer and the 4 pins of the RJ-11, direct physical or electrical connection of the RJ-11 to the computer is not possible.
Consequently, it has been found necessary to employ modems or similar input/output devices or cards to effect communication between computers and telephone lines. Modems reconfigure binary data from the central processing unit of the computer as received through the multi-pin peripheral port. The reconfigured data is then transmitted in analog form through the RJ-11 physical/electrical media connector into the telephone line.
In contradistinction to the development of telephone lines, transmission lines used in LANs have been developed specifically for the transmission of computer generated signals. Because of the recent development of these transmission lines, a variety of internal configurations for transmission lines have been developed to accomplish the transmission of computer data between computers.
A typical local area network comprises several computers at remote locations throughout a building interconnected with unshielded twisted pair cable utilizing RJ-type physical/electrical media connectors. The network is typically connected to a file server. A file server is a computer providing shared access to a file system, printer, electronic mail service, or modem. The file server is a combination of hardware and software that contains files shared by everyone connected to the LAN.
As LANs utilizing unshielded twisted pair cable are capable of transmitting signals at a higher rate than signals traveling through telephone lines, the requirements of the devices used to translate and reconfigure signals from the computer for transmission through lines have consequently been developed with different requirements.
The counterpart to the modem in telephonic communications is the LAN adapter card or data communications card. In a similar fashion to a modem, these communications cards reconfigure the parallel data produced by the computer into a serial form and back. These cards also provide buffering, encoding and decoding, cable access, and transmission.
As the use of LANs increases, it has become increasingly more beneficial for users of portable computers to have the ability to interact with several local area networks at different locations. For example, information at one location may be downloaded to a portable computer that allows a user to manipulate the data during a business trip and load the manipulated data onto the network at a destination. Diagnostics and maintenance are also made easier through the use of common connectors.
As the popularity of twisted-pair cable has increased, the popularity of the most frequently used physical/electrical media connector, the 8-pin miniature modular plug, has also increased. This increase in popularity of the 8-pin miniature modular plug has introduced the same problems and solutions into LANs as will be discussed regarding the RJ-11 physical/electrical media connector in the development of modems.
Many modems in use today are configured as external accessory units, housed in their own cases, and attached to the computer. Typically, external modems are electrically connected to the telephone with a telephone extension line utilizing physical/electrical media connectors at each end. External modems are often employed by users of personal computers because they can easily contain a substantial amount of electronic circuitry or hardware, as well as executable programs or software.
With the advent of downsizing technology in computer components, however, smaller portable computers (often referred to as laptop or notebook computers) have taken the place of many of the desktop models which use external modems. With the new-found portability available with laptop or notebook computers, the size of external modems has proved cumbersome and been rendered obsolete in keeping with the portability that buyers of these downsized computers desire.
To overcome the inconvenience and physical limitations of external modems, smaller modems have been developed that are small enough to be built integrally within the housing of a portable computer. As a result, integral internal modems that interface with the ubiquitous RJ-11 system provides users of portable computers with internal modems having a uniform standard interface for media access devices such as modems. Now, modem manufacturers can build products capable of accepting the RJ-11 media connector with confidence that their product can be used in a wide geographical area. Because modems can be built to the RJ-11 uniform standard, consumers benefit from the ability to interchange and interconnect media access devices without the need for adapters for products made by different manufacturers.
As computer housings have continued to be downsized, internal spatial restrictions have required the establishment of standards for the internal accessories of the computer. One set of standards applicable to memory cards has been developed by the Personal Computer Memory Card International Association (PCMCIA). This organization is comprised of hundreds of manufacturers of memory cards and related peripheral equipment. By convention, the PCMCIA has determined that the spatial standard for all memory cards used in down-sized computers should be restricted to a rectangular space approximately 55 mm in width, 85 mm in length, and 5 mm in depth.
In keeping with the PCMCIA standards for memory cards, internal modem manufacturers have adopted the same spatial standards for use with their down-sized communications cards such as a communications card 12 of FIG. 1. By complying with the standards established by PCMCIA for memory cards, communications card manufacturers have assured themselves of compatibility and spatial conformity with a computer 10 utilizing the new PCMCIA standards.
The constraints imposed by this new PCMCIA standard have resulted in the development of "credit card" communications cards. Most of the components formerly housed within a modem are now contained within a credit card-sized device. Although many of the communication cards serve the functions of a modem, a similar card has been contemplated for use in LANs. Nonetheless, the problem will hereinafter be addressed in terms of the PCMCIA standard communications card.
Since the depth of a PCMCIA standard communications card is limited to 5 mm and the depth of a typical media connector, such as the RJ-11 type or 8-pin miniature modular plug, is approximately 8-12 mm, the typical media connector exceeds the depth restrictions imposed by the PCMCIA standards for internal computer components.
While many prior art devices have tried to solve the depth incompatibility problem between the PCMCIA standard communications card and the media connector, a "pop-out" or sliding interface device 14 has emerged as a popular solution. The pop-out interface device, known commonly as the XJACK.RTM. initially produced by MEGAHERTZ Corp., now owned by 3 Com Corp., solves many of the interface problems posed by prior art devices. Such solved problems include, but are not limited to: (i) the elimination of carrying along an extra interfacing device compatible with both the media connector and the PCMCIA communications card; (ii) the elimination of ensuring a DAA in the interfacing device is compatible with the computer; (iii) the elimination of physical interference between adjacent PCMCIA communication cards in adjacent slots when the PCMCIA communication card has an enlarged portion thereof larger than the conventional 5 mm thickness; (iv) the elimination of potential breakage of the interface connector when not in use; and (v) the elimination of protrusions beyond the normal dimensions of the computer so that the computer portfolio is more compatible with devices typically transporting laptop computers.
With reference to FIG. 2, a typical embodiment of a sliding interface device in the form of a conventional 5 mm thick PCMCIA-architecture style communications card for directly interfacing with a media connector is depicted generally as 20. The communications card 29 defining the interface device 20 has a retractable access portion 22 and a fixed portion 24.
The fixed portion 24 is in electrical communication with a computer (not shown) by means of electronic circuitry connected on a printed circuit board (PCB) housed internally within the communications card 29. For brevity, fixed portion 24 may sometimes be referred to as the PCB 24 although the fixed portion includes more than just the PCB and electronic circuitry. The retractable access portion 22 is in electrical communication with the fixed portion 24 through a flexible wire ribbon 30. During use, in means well known in the art, the retractable access portion 22 slides in and out of a slot 32 formed within the PCB 24. The retractable access portion 22 is urged out of the slot 32 by a spring 34 biased, in a direction external to the computer housing, by a ledge 36 connected to the PCB 24. Although not shown, the computer housing during use is substantially parallel to an edge 37 of the communications card 29. A limiting notch 42 engaged by a biased lever 40 is used to restrict the travel distance of the interface device to a predetermined distance when the retractable access portion is urged in a direction external to the computer housing by the spring 34. After use, a retention notch 38 in combination with the biased lever 40 is used to retain the retractable access portion 22 within the housing of the computer.
An aperture 44 having a plurality of walls 46 is formed within the retractable access portion 22. The aperture 44 is so sized and shaped as to be capable of receiving a physical/electrical media connector. Formed within aperture 44 by means of walls 46 is a broad retention clip groove 48, a narrow retention clip groove 50, and a retention ridge 52. These structures within aperture 44 provide for the retention of a connector pin block of a physical/electrical media connector. A guide track 54 is formed within communications card 29 protruding upwardly from the bottom of communications card 29. Guide track 54 is interengaged with a corresponding guide groove formed in the bottom of retractable access portion 22.
When a user desires to connect a telephone line to the communications card, biased lever 40 is manipulated out of retention notch 38. As retractable access portion 22 is released from the grip of biased lever 40, tension applied by spring 34 urges retractable access portion 22 out of slot 32. The progress of retractable access portion 22 is guided by guide track 54 and is halted when biased lever 40 engages limiting notch 42. A user then inserts a physical/electrical media connector into aperture 44 to provide an electrical connection between communications card 29 and the telephone line. When a user no longer desires to access the retractable access portion 22, the user merely presses retractable access portion 22 back within the confines of the computer housing until the retention notch 38 is engaged by biased lever 40.
While the example as described has been effective as a media interface connection, safety precautions and requirements frequently emerge as products gain widespread public acceptance and safety consciousness increases. It is well known that public telephone transmission lines and electrical power transmission lines either share common conduction line supports such as "utility poles" or are adjacently positioned on individual utility poles. Additionally, both electrical and telephonic transmission lines are adjacently located as they enter into an end user's structure such as a home or business. As such, there exists the potential for both conduction lines to contact each other when in their conductive state thereby causing interruptive and dangerous conditions on the other's conduction lines. For example, telephonic lines, and in particular Public Switched Telephone Network (PSTN) lines, generally transmit signals using Direct Current (DC) signalling using approximately 48 volts with current levels around 120 m A or less. In contrast, electrical or power conduction services generally transmit power using Alternating Current (AC) techniques and utilize voltage signal levels of hundreds and even millions of volts with current levels in the hundreds to millions of amperes range. In the eventuality that both the electrical or power transmission lines were to contact the telephonic transmission lines, large and hence dangerous signal levels on the telephone lines could subject individuals and equipments such as modems and computers to injurious and fatal conditions.
Other potentially dangerous failure modes include spurious lines conditions that exceed expected transmission ranges. For example, the telephonic transmission lines of the PSTN system, as described above, accommodate a voltage in the range of 0-200 volts when the "ring voltage" is sent across the lines. Equipments such as communications cards are designed to accept such signal levels. However, when acts, including acts of nature such as lightning strikes, introduce transient conditions in excess of hundreds and even thousands and millions of volts that reach injurious levels for both humans and equipments.
To moderate such occurrences, requirements by safety agencies have been promulgated to manufactures of interface devices such as communication cards, including modem and network cards, to provide protection against injury and damage from such calamity. In many instances, the safety requirements are scheduled to be in place on communications cards by the year 2000. On such safety requirement dictates that end user equipment such as communication cards must provide a removable fusible link that will activate upon the occurrence of conditions commensurate with 600 volts and 40 amperes. Such requirements accommodate the typical operational conditions utilizing the PSTN standard and other similar defined standards. While the precise specifications of the safety requirements vary between countries and agencies, the general nature of the regulations includes providing a spurious line condition protection mechanism for the protection of both the human communications card end user as well as the communications card equipment itself.
Accordingly, it would be an advance to provide an improved electrical connection between the media connector, such as the telephone or network interface, and the communications card or communication or computing device that substantially provides the protection to both end users and the equipment itself as requested by safety regulations.